1. Field of the Invention
The present invention relates to a cleaning unit used in an image forming apparatus, such as a copying machine or a laser printer, which uses toner for forming images.
2. Description of the Prior Art
It is generally known that a full-color copying machine is provided with a belt-like recording medium onto which toner images of different colors developed on a photosensitive material are transferred. In such a copying machine, a cleaning unit having a cleaning head for removing residual toner from the surface of the recording medium is disposed movably with respect to the recording medium.
In a conventional mono-color copying machine, since there is no need to superimpose toners of different colors onto a belt or the like, it is not necessary to provide the recording medium. The cleaning head need not be switched between two positions, that is, a contact position and a release position with respect to the recording medium.
Also, even in the case of a full-color copying machine, if the construction is such that different color images are superimposed one on top of the other directly onto the copy paper, it is not necessary to clean the recording medium.
On the other hand, in the case of a full-color copying machine which uses a recording medium, it has been a usual practice to always press and release a cleaning head with the same timing regardless of any change in the copying conditions.
In a full-color copying machine, when a cleaning head is separated from a recording medium while cleaning the recording medium to remove residual toner, there is a possibility that the toner adhering to the cleaning head may fall onto the recording medium and adversely affect the image quality.
Also, since the cleaning head is always separated from the recording medium at the same position on the recording medium regardless of any change in the copying conditions, the problem is that the toner falling off the cleaning member may be deposited onto the image area on the recording medium depending on the copying conditions, allowing the deposited toner to be transferred to the copy paper and thereby smearing the copy image.